The mammalian fetus utilizes glucose as a principal energy source, yet is dependent on preformed glucose supplied by placental transport. During immediate extra-uterine adaptation, the newborn is required to independently regulate blood glucose concentration. The objectives of this proposal are: 1) Delineation of the role of fetal hepatic glycogen in the autoregulation of blood glucose in the fetus. 2) Determine the relationship between glucagon and cyclic AMP in the precocious induction of phosphoenolpyrurate carboxykinase activity in the fetus. 3) Define the role of lipolysis and fatty acid oxidation in regulating gluconeogenesis during the newborn period. 4) Determine the relationship between activity and apoenzyme concentration of PEP-CK under different experimental conditions.